That’s because you are visiting your website using a web address that’s different from the one you have set in your RapidWeaver project. Possibly a www difference.
Please update your RapidWeaver Project web address accordingly and republish the page.

You have set Stacks Store URL to http://www.betastacks.com/store/rcp/index.php in Customization > Settings > General window.
The page doesn’t exist.
Please set it to the stacks page that actually contains RapidCart Pro Store stack.